Controllable Wettability Of PMIA Nanofibrous Membrane For Oil/Water Separation

Oil/water separation is a process of separating oil and water using the methods, techniques and equipment. Traditional treatments for oil/water separation have gravity separation, coalescence, thermochemical treatment process, air-floating method biologic method etc. However, they have kinds of shortcomings like consumed lots of energy, long cycle. In some cases, water has been polluted by chemical additive. In recent years, membrane separation method have attracted more and more attention as an efficient technique which can save energy and be friendly to environment. Efficient oil-water separation membrane hould be with high porosity and appropriate surface wettability. Generally, hydrophobic membrane is easy to cause oil pollution, and also hydrophilic membrane has poor mechanical strength. Super-hydrophobic membrane interface are being widely studied because it can overcome the above disadvantages.In this research, nanofibrous membranes with superhydrophobic and superoleophilic properties and high porisity have been fabricated for oil-water mixture separation through combination the electrospinning and in-situ polymerization techniques. Electrospinning has been shown to be a simple but powerful technique for the preparation of nanoscale levels fibers. Electrospun fibers are much thinner in diameter and thus higher in surface-to-volume ratio. These fibers are also extremely long and thus can be assembled into a three dimensional mat. All pores are fully interconnected and this make benefit for liquid transportation on the membrane. So, the research used electrospinning to fabricate separation membrane. Conventionally, there are two approaches to produce the superhydrophobic surfaces:one is to modify the surface with low surface free energy material on the rough surface, the other is to create rough surface on the low surface free energy. The polybenzoxazine (PBZ), a newly developed class of low surface free energy materials with a wide range of interesting features including flexibility in the molecular design. In this research, a new kind of PBZ was synthesized by solvent-free method. The curing behavior can be happened at specific temperatures, which make it form a hydrophobic cross-linked thermosetting polymer layer. So, first a novel fluorinated surface (FPBZ) modified nanofibrous membranes, which make membrane became hydrophobic and then incorporated SiO2nanoparticles (FPBZ/SiO2NPs) functional layer, which make hydrophobic membrane became superhydrophobic and oleophilic become superoleophilic.It shows that the research has successed to fabricate superhydrophobic and superoleophilic nanofibrous membranes for oil/water separation. The content of BAF-oda monomer and SiO2nanoparticles have been proved to be the key factor affecting the fiber surface free energy and roughness. When the content of BAF-oda and SiO2is lwt%and2wt%, the pristine hydrophilic PMIA nanofibrous membranes are endowed with the promising superhydrophobicity with the water contact angle of161°and a superoleophilicity with the oil contact angle of0°. This new membrane shows high thermal stability (350℃) and maintained promising hydrophobicity of143°after the annealing treatment, and good repellency to hot water (80℃), and achieving the excellent mechanical strength of40.8MPa, more interestingly, after calcination at300℃for10min, the FPMIA-1/SNF-2membranes still maintained comparable strength of21.1MPa. In addition, the FPMIA-1/SNP-2membranes exhibited robust superhydrophobicity towards water with a broad range of pH, showing excellent stability and usability. Furthermore, the as-prepared membranes exhibited fast and efficient separation for oil/water mixtures by solely gravity driven, which makes them a good candidate in industrial oil-polluted water treatments and oil spill cleanup, and also provided new insight into the design and development of functional nanofibrous membranes through FPBZ modification.